1. Field of the Invention
The present invention relates to a flat cathode ray tube, and more particularly, to a panel/shadow mask assembly in a flat cathode ray tube assembled together by a rail fastener.
2. Background of the Related Art
In general, the cathode ray tube is used for displaying an image on a TV receiver, or monitor, of which flat cathode ray tube has an increasing demand because the flat cathode ray tube has improved performance, such as provision of a picture close to an actual image, and significant eye fatigue reduction. A system of a related art flat cathode ray tube will be explained, with reference to FIG. 1.
The panel/shadow mask assembly in the flat cathode ray tube is provided with the panel 1, a rail fastener 7 disposed along a periphery of the panel, and a shadow mask fastened to the rail fastener 7. In detail, there is a fluorescent film 1a of R, G, B three colors coated on an inside surface of the panel 1 in a fixed pattern, and a flat explosion proof glass 2 bonded with resin on an entire surface of the panel 1 for explosion prevention. And, there is a rectangular frame of a metal rail fastener 7, means for fastening the shadow mask 8, bonded with frit glass to an inside periphery of the panel, to a surface thereof facing a funnel 3 a shadow mask 8 of a metal having a plurality of holes 8a for passing electron beams 5 is welded under a pretension. There may be an inner shield 9 for shielding a geomagnetism and damping wires(not shown) for suppression of vibration of the shadow mask 8 fastened to the rail fastener 7. And, there is the funnel 3 having a neck portion 4 of a bottle neck form bonded with frit glass to a rear surface of the panel 1, with a cavity formed thereby at a high vacuum approx. 10xe2x88x927 Torr, and the neck portion 4 has an electron gun 6 built therein for emitting the R, G, B three color electron beams 5 toward the inside surface of the panel.
In the foregoing flat cathode ray tube, if an image signal is provided to the electron gun 6 sealed in the neck portion 4 of the funnel 3, the electron beams 5 are emitted from cathodes. Then, the emitted electron beams 6 are controlled, accelerated, converged by voltage differences between voltages provided to respective electrodes in the electron gun 6, involved in locus change in a horizontal and vertical directions by an electro-magnetic field from a deflection yoke 10, pass through the holes 8a in the shadow mask 8, and cause the fluorescent film 1a coated on the inside surface of the panel 1 to emit light. As the foregoing series of steps are taken in succession, the flat cathode ray tube can reproduce the image.
In the meantime, the rail fastener 7 has long side rails 7a and short side rails 7b put together by end caps 7c into the rectangular frame for use in assembling the panel/shadow mask. Particularly, as shown in FIG. 2, the rail fastener 7 used the most widely has a section provided with an injection groove 7d on a side of the rail fastener 7 facing the panel 1 for injection of frit glass 11 and a welding surface 7e on an opposite side thereof for welding with a periphery of the shadow mask 8. Other than this, as shown in FIGS. 3Axcx9c3D, there are rail fasteners 7 with different types of sections are used for the panel/shadow mask assembly.
The following steps are taken for fabricating the assembly of the panel 1 and the shadow mask 8 by using such a rail fastener 7.
Frit glass powder is mixed with liquid into a gel, and injected into the injection groove 7d in the rail fastener 7 which is clean beforehand for a few times with the frit glass divided equally, and left until the frig glass is hardened. Next, under a state, top frit glass is injected on the already hardened frit glass 11 additionally, the panel 1 and the rail fastener 7 are aligned and welded, to bond the panel 1 and the rail fastener 7 together and to seal between the panel 1 and the rail fastener 7 by the bonding force of the top frit glass. Then, the welding surface 7e of the rail fastener 7 is ground flat for welding the shadow mask 8 to the panel 1 with a uniform gap therebetween. After a fluorescent material is coated in a region of the panel surface on an inner side of the rail fastener 7, exposed, and developed to form the fluorescent film 1a of a fixed pattern, the shadow mask 8 is given pretension in four directions before the shadow mask 8 is welded to the welding surface 7e of the rail fastener 7. In this instance, during the coating, exposure, and development, the panel 1 is washed for removal of impurities in a state the rail fastener 7 is attached thereto.
However, as shown in FIG. 4, in the related art rail fastener 7, since the flat inside surface of the related art rail fastener 7 is substantially vertical to a flow direction of the washing water (an arrow direction in FIG. 4), the washing water sprayed to an inner side of the rail fastener 7 can not be discharged to outside of the rail fastener 7 smoothly, but flows reversely into the inner side of the rail fastener 7 as the washing water hits onto the inside surface of the rail fastener 7. Consequently, foreign matters at corners of the rail fastener 7 are not washed away perfectly, but remained in gaps between the rail fastener 7 and the panel 1, that vaporizes, resulting to drop the vacuum. And, provided the foreign particles fly into the electron gun 6, the electron gun will cause discharge, and provided the foreign particles fly into the shadow mask 8, the foreign particles will block the holes 8a through which the electron beams 5 to pass through, that causes defects in products. Particularly, as larger sized cathode ray tubes are fabricated, a thickness xe2x80x98xcfx84xe2x80x99 of the rail fastener 7 also becomes thicker proportionally, to deteriorate an efficiency of foreign matter removal by using the washing water further. Besides, the fixation of the rail fastener 7 to the panel 1 by using frit glass requires many steps, that is not favorable for productivity and price competition.
An accurate design for bonding the panel 1 and the rail fastener 7 is required as flit glass shrinks in hardening, and pores in the frit glass may drop an internal vacuum of the cathode ray tube, as the pores may discharge the air therein.
Accordingly, the present invention is directed to a panel/shadow mask assembly in a flat cathode ray tube that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a panel/shadow mask assembly in a flat cathode ray tube, which can improve a washing efficiency of foreign matter formed in a process of fabricating a cathode ray tube.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the panel/shadow mask assembly includes a substantially flat panel having an effective surface with a coat of fluorescent material thereon, a rail fastener fitted to a periphery of the panel wherein a surface of the rail fastener on a side of the effective surface of the panel has a radius of curvature, and a shadow mask fixed to the rail fastener under pretension.
The radius of curvature of the surface of the rail fastener on the side of the effective surface of the panel is preferably within a range of 4 mmxcx9c40 mm.
The panel and the rail fastener are bonded by using frit glass, and preferably by electrostatic bonding.
Thus, the present invention can prevent a quality deterioration of a flat cathode ray tube caused by foreign matter, and save production time and cost.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.